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Abstract

Multicolor femtosecond pulses were simultaneously obtained by a cascaded FWM process in fused silica glass. The sideband spectra were tunable by changing the crossing angle of the two input beams. Frequency up-shift and down-shift pulses with energies as high as 1 μJ, durations of 45 fs, nearly diffraction limited Gaussian spatial profiles, and power stability smaller than 2% RMS of the generated sidebands were obtained. These multicolor sidebands can be used in various experiments, such as multicolor pump-probe experiment.

Figures (6)

The input pulse duration and phase of beam1 (dashed lines) and of beam2 (solid lines). The inset patterns are the two-dimensional beam profiles of beam1 (lower) and beam2 (upper) on the surface of the fused silica glass.

(a) The spectra of the sidebands from S1 through AS5 and of the two input beams when the crossing angle between the two input beams was 1.87°. (b) Spectra of AS3 at crossing angles of 1.40°, 1.64°, 1.87°, 2.10°, 2.34°, and 2.57°. The photograph at the top of Fig. 2(a) shows the sidebands on a sheet of white paper placed 30 cm after the glass plate when the crossing angle between the two input beams was 1.87°. The first, second, and third spots from the right edge are S1, beam2, and beam1, respectively.

Dependence of the angles between the generated sidebands and beam2 (with 0 order number) on the order number of the sidebands when the crossing angle between the two input beams was 1.40°, 1.64°, 1.87°, 2.10°, 2.34°, and 2.57°. Order number -1 refers to S1, 1 refers to AS1, and so on.

(a) Dependence of the output power on the order number when the crossing angles between the two input beams were 1.40°, 1.87°, 2.10°, and 2.57°. Order number -1 refers to S1, 1 refers to AS1, and so on. (b) The stand deviations of AS1 and beam1, as monitored over four minutes, were 1.82% RMS and 0.97% RMS, respectively.

The two-dimensional spatial modes of (a) S1 and (b) AS3. (c) The one-dimensional spatial profiles of S1 and AS3, together with a Gaussian fit to S1. The two-dimensional spatial mode of beam2 (d) when beam1 was blocked and (e) when the input power of beam1 was 20 mW.